1. Field of the Invention
The present invention relates to a cover stitch sewing machine, and more particularly to a cover stitch sewing machine in which at the time of sewing with a fine stitch pitch, when a needle thread take-up runs out needle threads by lowering a plurality of needles, the needle threads are taken up due to the elasticity of a needle thread pulling-up spring thus preventing the occurrence of a slack of the needle threads which extendedly exist below needle thread eyes whereby a double chain stitch seams having no skips are formed.
2. Description of Related Art
Conventionally, there has been known a cover stitch sewing machine in which a plurality of needle threads are supplied to a plurality of needle thread eyes of a plurality of needles by way of a plurality of needle thread tensioning devices and a needle thread take-up, a looper thread is supplied to a looper from a thread spool by way of a looper thread tensioning device and a looper thread take-up, and a cover stitch of double chain stitch seams is formed in a sewing material on a needle plate due to the intertwining of the needle threads of the respective needles and the looper thread of the looper in response to a cooperative operation of the plurality of needles and the looper (see Japanese Patent Laid-open 2000-93671).